Wednesday, September 15, 2010

Buffer Cache Hit Ratio

Tuning the buffer cache hit ratio

A logical read occurs whenever a user requests data from the database. It occurs whenever the data is in the buffer cache or whether the user process must read it from disk. If the data must be read from disk then a physical read occurs. Oracle keeps track of logical and physical reads in the V$SYSSTAT table.

Use the following SQL statement to determine the values required for the hit radio calculation: